The present invention pertains to improvements in cross connect panels, and in particular to the type of cross connect panels adapted for controlling lighting installations, for example stage lighting in a theater.
In a typical installation it is necessary to provide some means for interconnection between a plurality of variable power dimmer controls on the one hand, and a plurality of lamps or sets of lamps whose intensity is to be controlled, on the other hand. Because different stage productions require different types of lighting control, it is generally considered necessary that the system be readily programmable so that any particular set of lights can be controlled by any given dimmer, as may be required for a particular stage production. This requirement for maximum flexibility has generally precluded permanent or semi-permanent interconnections whereby each dimmer control would be dedicated to a given set of lights. Accordingly, cross connect panels have been provided to supply the necessary interconnection flexibility.
Cross connect panels generally comprise a matrix of buses or rails, with a first set of parallel buses in one plane, and a second set of parallel buses at right angles to the first set and spaced a short distance from them so that there is normally no electrical contact between two sets of buses. A plurality of sliders are provided, usually one for each of the buses in one of the sets of buses. The sliders contain contacts for making an electrical circuit between the bus on which the slider is mounted, and any of the buses perpendicular thereto, depending upon the positioning of the slider. Any of the loads can be connected to any of the dimmers simply by proper positioning of the sliders.
Although prior art cross connect panels have met with success, they have been subject to a number of problems which have tended to limit their performance and increase their cost. Because of the very high amperages involved, the slider mechanism which actually makes the interconnections must be very carefully designed to make positive and secure electrical contact so as to prevent arcing between the slider contacts and the buses. At the same time, means should be provided to insure that a number of unwanted circuit connections are not momentarily made when the slider is being moved from one position to another. Although prior art bus bars are recessed in channels between protruding insulators for spark suppression, still it is all too possible for the contact of prior art sliders to bounce across the protruding insulators and hit every bus bar during a change of position of the slider.
Another problem with prior art cross connect sliders is the uncertainty of positioning when an operator is moving the slider to a new position. Because of the close spacing of the buses, it is often necessary in prior art devices for the operator to adjust the final position by "feel" which of course creates the possibility of further arcing, or inadvertent connection to the wrong bus.
Because of the high currents involved, it is generally necessary to construct the conductors from elongated metal bars of substantial thickness. A sandwich structure is often made with alternating layers of insulating pieces and bus bars. The problem then becomes one of how to hold the sandwich together. Problems exist in some prior art devices because insufficient pressure has been used to hold the stack together, with the result that inadvertent downward pressure applied to a slider might bow or bend a bus bar out of line, or split them apart, wedging the slider contact. Another method of holding the bus bar/insulator stack together involves drilling holes through each piece so that they can be bolted together. Although this method yields a workable structure, it leads to extra expense in drilling of the bus bars, and providing insulating grommets for each one to prevent them from shorting out on the bolt. Also, since the holes drilled out from the bus bar reduce its current carrying capability by drastically reducing the effective cross sectional area at the hole, it has generally been necessary to provide very thick or wide bus bars to compensate, leading to further great expense.
To overcome these and other problems existing in the prior art, the present invention provides an improved cross connect panel.